Process and apparatus for making corrugated tubes



M. KNAB Dec. 4, 1934.

PROCESS AND APPARATUS FOR MAKING CORRUGATED TUBES Filed April 2, 1950 5 SheetsSheet 1 IIVVEN'TOR.

A TTORNEYS.

Dec. 4, 1934. M. KNAB 1,983,468

PROCESS AND APPARATUS FOR MAKING CORRUGATED TUBES Filed April 2, 1930 3 Sheets-Sheet 2 INVENTOR.

A TTORNEYS.

M KNAB 1,983,468

PROCESS AND APPARATUS FOR MAKING CORRUGATED TUBES Filed April 2, 1930 5 Sheets-Sheet 3 77(W if ma INVENTOR.

By $711 7 F6 A TTORNEYS.

Patented Dec. 4, 1934 PATENT FFlCE- T PROCESS AND APPARATUS FOR MAKING: CORRUGATED TUBES Max Knab, New York, N. IL, assignor to Spragne Specialties Company, Quincy, Mass a corporation of Massachusetts Application April 2, 1930, Serial No. 441,128 20 Claims. (01. 152-71) My-invention relates to the manufacture of corrugated tubes and more particularly of thinwalled tubes provided with corrugations, and embraces the novel means and processes of making the same.

One special application of my invention is that to the manufacture of corrugated tubes of filmforming metal, as aluminum, to be used as anodes for electrolytic condensers and similar devices,

and I shall describe my invention in connection with the manufacture of such tubes.

The dielectric capacity of a condenser of the electrolytic type is directly proportional to the area of the anode. It is evidently of great advantage if a large anode area can be combined with a small volume, and therefore, it has been proposed in the copending application of F. Desmond Sprague and R. U. Clark, Ser. No. 416,939, filed December 27, 1929, to use for anode a thinwalled tube of film-forming metal having corrugations in the form of a helical screw-thread.

Such an anode in addition to combining a large area with a. small volume, has the advantage of a strong and rigid structure, relatively small ratio of edges to surface, can be constructed from a single piece of metal, and has other advantages fully described in the above-referred-to application.

When endeavoring to manufacture anodes of the type referred to by various methods suggesting themselves, great difficulties have been encountered. For instance, by inserting a threaded arbor in the tube and exerting pressure simultaneously on the full length of the tube, it has been found that the aluminum would break as the depth of the corrugation exceeded a certain limit. For instance, in a tube having a diameter of 1%", a length of 6", a wall thickness of'.020 and about 3% threads per inch, difflculty is en- 40 countered in case the depth of the corrugation is to exceed 1%".

This is due to the fact that the material is stretched in suchoperation and above a certain limit determined by the tensile strength of the K aluminum, the material will break. But even if the depth of the corrugation is kept below the limit of actual rupture of the material, deformation of the tube will prevent the wall from being uniform in thickness and in strength.

To obtain satisfactory results, I have found it necessary to form the corrugations progressively, so as to enable the excess material required for the corrugations to be freely drawn from the tube. I have found that in placing the tube on a rotating screw arbor and gradually rolling the tube around this arbor by means'of a laterally moving roller, corrugations of considerable depth could be obtained with small or no distortion of the tube. Thereby I found that to obtain satisfactory results the full required depth of the corrugations should be achieved by a single rolling operation, and subsequent rolling operations,

it any, should be restricted to the smoothing out of possible wrinkles in the corrugations without endeavoring to deepen them.

I have found, furthermore, that by using a tensioned wire, instead of a roller, still better results. could be obtained and that by gradually winding such a wire around a tube when placed on a rotating screw arbor, corrugations of practically any desired depth can be obtained without distortion of the material and without change in the wall thickness of the tube.

The advantage of using a tensioned wire as compared with a roller is due to the following facts: (a) The wire permits a smaller contacting area than the roller and therefore conforms precisely to the shape of the thread. (b) The" line contact of the wire permits more freely the material to be drawn from the free end of the tube than in case of a roller. (0) The wire wound' around the threaded portions of the tube forms a tight grip around these portions.and prevents their deformation during the further threading of the tube.

It should be well understood that my process of corrugation is basically different from any known method of spinning or like process previously used for the corrugation of metal tubes. In these methods the metal is stretched, whereas in my process the material is allowed to freely flow and twist around the arbor, whereby the total surface of the tube as well as the tube thickness is the same before and after corrugation.

While with the wire threading process, as above outlined, I have found that corrugations of any corrugations, I have found it desirable to subject 10() tubes corrugated by either one of my above illustrated processes, to a novel compressing method by means of which the corrugations can be closed upto any desired pitch. It should be understood that my compressing process is independent of the type of corrugations incorporated in the tube to be collapsed as well as of the process by which the corrugations have been effected.

In this compressing process, I employ a device including a compressing fixture and spacing means to limit the compression of the corrugations to a predetermined and uniform limit, which in the case of anodes for electrolytic condensers is determined by the clearance required for the free circulation of the electrolyte between the corrugations both on the inside and the outside.

I have also found that it is of advantage to subject the corrugated tube after its corrugation but before its compression to a roll ng process so as to smoothen out undesired wrinkles which have been effected in the corrugation process.

I may, if desired, correlate the corrugating and smoothing processes in associated operations.

From the above, it will appear that one of the objects of my invention is to provide a method of manufacturing corrugated tubes having deep corrugations and uniform wall thickness.

A further object of my invention is to provide a method of corrugation, whereby the tube is placed on a mandrel and the corrugation formed on the tube by progressive pressing or rolling operation.

A further object of my invention is to provide a method of corrugation whereby a screw arbor is rotated and the tube material is caused to freely flow in the threads of the arbor.

A further object of my invention is to provide a method of corrugation whereby the total surface area'of the tube is the same before and after corrugation and the wall thickness of the tube remains unchanged.

A further object of my invention is to provide a method of corrugating a tube on a rotating screw arbor by forming the tube to the shape of the arbor by the means of a tensioned wire progresslvely wound around the tube.

A further object of my invention is tosmoothen out the corrugations formed as above set forth, by a subsequent and preferably correlated rolling operation.

A further object of my invention is to compress the corrugated tube by a pressure-operated compressing device, whereby spacing means are provided to limit both the outside and inside closing-up of the corrugations to a desired and fixed dimension.

Further objects of my invention will appear as the specification progresses.

Referring now to the drawings, Figure 1 is a side elevation showing a tube to which my invention is to be applied.

Fig. 2 is a top view of Fig. 1.

Fig. 3 is a side elevation showing the tube of Fig. 1 after it has been corrugated according to a preferred method of my invention.

Fig. 4 is a side elevation of a tube as shown'in Fig. 3 after such a tube has been subjected to a compressing process forming part of my invention.

Fig. 5 is a side view of a tube in the process of corrugation, with the corrugating means schematically illustrated.

Fig. 6 is a side view showing a tube in the process of smoothing, subsequent to its corrugation, also showing the smoothing roller arrangement.

Fig. '7 is a perspective view of the holding head for the screw arbor.

Fig. 8 is a fractional side view showing the conical end of the screw arbor.

Fig. 9 is a top view of the compression device, partly in section and w'th parts broken away, with a corrugated tube therein prior to its compression.

Fig. 10 is a top view of the compression device with a tube after it has been compressed.

Fig. 11 is a fractional perspective view showing the left-hand end of the compression device in its closed position.

Fig. 12 is a perspective view of a spacer plate of the compression device.

A thin-walled aluminum tube 10 (Fig. 1) is open at its lower end and is provided on the other end with a conical head 11 having two locating holes 12-12. The head 11 extends in a tapered stem 13 provided with a beveled section 14 and a threaded end 15. On its lower end the stem 13 is provided with a center bore 15a to receive the bit of a, threaded arbor to be later described.

To corrugate such a tube by the preferred method of my invention, the.tube 10 (as shown in Fig. 5) is placed on a screw arbor or mandrel provided with a threaded portion 39-, a straight portion and a conical head 37; The conical head is also provided with a bit or pin 36 to lit in the center bore 15a of the tube, and with two locating holes 38-38 brought in juxtaposition with the holes 12-12 of the tube when the latter is slipped over the arbor.

The straight end 40 of the tube is provided with parallel flats 41-41 and a center bore 34.

The arbor 35 is placed on a lathe or similar device, which by proper gripping of the arbor permits rotation thereof at am desired speed. For the proper securing of the arbor there is provided on the left side a head 20 comprising a conical recess 27, locating pins 28-28 and a clearance bore 25 for the stem 13 of the tube. When inserting the arbor 35 and tube 10 in the head 20, the pins 28-28 project in the holes 12-12 of the tube and the holes 38-38 of the arbor, tying the arbor, tube and head together and thus preventing their relative displacement when the arbor is rotated.

On its other end the arbor is held by a laterally movable center 30 which when moved toward the arbor engages its center bore 34.

A wire '45, preferably of high grade steel, is anchored in the head 20 and guided in helical lead grooves 23 of the head 20 towards the tube 10. The end of the head 20 is cut away at 24 permitting smooth transition of the wire from the head to the tube.

From the head 20 the wire 45 is led over a pulley 46 and is properly tensioned by the combination of a spring 49 and a weight 48, as more fully explained hereafter. As the head 20 is rotated manually or preferably by motor power, the tube 10 and arbor 35 are rotating therewith and the wire is gradually wound around the tube and forces the latter to assume the corrugations determined by the thread of the arbor (as shown in Fig. 5 to the left of the line X-X) whereby on the threaded portion of the tube the wire forms a tightly gripping helix lying in the root spiral of the thread.

It should be well understood that the wire is of suflicient length to be wound around the whole length of the tube and at the same time to permit location of the pulley 46 and of the tensioning means at any convenient distance from the arbor.

I have found in practice that it is advantageous not to place right from the start the full tension on the wire, but preferably to increase gradually and uniformly the tension of the wire from zero to its ultimate value during the forming of the first thread.

For this purpose, I connect the free end of the wire 45 with a rod 51 carrying a plate 50. On top of the plate and placed within a spring cylinder 4'? is a coil spring 49 which is gradually compressed as the wire winds around the tube '10 and the plate 50 thus lifted. 1

. The spring cylinder 47 carries at its lower end the. weight 48, which rests on a suitable base when the threading is started. During the winding of the first thread the spring 49 is compressed to the value corresponding to the weight 48 and the weight now lifted so that in the-further threading operation, the wire is subjected toaflxed tension corresponding to the weight 48.

It should be noted that as the threading progresses the excess material required for the corrugations is drawn fromthe free end of the tube. This results in a corresponding shrinkage of the total length of the tube whereby, however, the metal is not stretched and the total area of the tube and the thickness of the tube remains unchanged.

It should also be noted thatin'my method of corrugation, the metal as it is caused to flow to fill out the threads of the arbor, is also subjected to a torsion or twisting action.

The twisting effect on the tube can be observed from Figs. 1 and 3, which indicate that a line a-d-shown in dotted lines-drawn parallel to the axis on the tube 10 before corrugation (see Fig. 1) assumes through the process of corrugation the angular position shown in Fig. 3, as line a'-a'. For instance, in the case of a tube having a diameter of 1%" a length of 10" and a wall thickness of .015", corrugated with a thread having a pitch of 3% threads per inch and depth, this twisting amounts to about three-quarters of a turn for the full. length of the tube. v

It should also be noted that in my corrugating method the required depth of the corrugation should be obtained by a single, rather than a plurality of threading operations, as once the tube is corrugated free flow of the material will no more take place.

As during the wire threading process, a slight amount of wrinkling of the tube takes place (as shown in an exaggerated manner in Fig. 5), I prefer to smoothen out these wrinkles by a subsequent rolling operation.

This operation, I prefer to correlate with the wire-threading process and for this purpose, I provide a roller 55 of a shape conforming with the threads of the arbor and rotatably supported on a pin 56 carried by a stirrup 57. The roller 55.

is brought in engagement with the tube when rotation of the head 20 is reversed to unwind the wire 45 from the tube. The roller stirrup 57 has an extension 58 inserted in a movable pivot 59 which is carried by the lathe-carriage in a lateral direction and at a rate corresponding to the rotation of the arbor. The pressure exerted by this roller is suitably adjusted and as shown in Fig. 6, the roller follows the unwinding wire whereby preferably a lag of one or two threads is provided between the wire and the roller. It should be also understood that sufficient play is provided in the roller support to permit free alinement of the roller 55 with the corrugations of the tube.

After the tube has been threaded and rolled, it is removed from the lathe and unscrewed from the'arbor, manually or by motor driven means.

' Fig. 3 shows the tube 10a after the threading and rolling operation.

Instead of using the wire-threading process,

I previously described, for the corrugation of the However, I prefer to use this method, only in thecase of shallow corrugations for reasons previously stated.

In using a roller to form the corrugations, -a

second roller preferably. of slightly diiferentshape may, if necessary, be employed for the smoothing out of the corrugations. However, it shouldbe noted that the full depth of the corrugation is-to be obtained with the first roller and the function of the subsequent roller, as stated, is only-"the smoothing out of the corrugations. 1

Taking up now the compression device above referred to, this comprises a two-part base-block 6565" (Fig. 11), hingedly connected at 80. and provided with a hook 81 to hold the. two parts together during compression. The respective parts 65-65 of the base are provided with recesses and cavities which in the closedcondltion of the base form a conical depression 66, and a connecting hole 67 to receive the head12 and the stem 13 of the tube. Two pairs of'guide rods 69-69 and 69'-69 are anchored in the upper block 65 and lower block 65' of'the base respectively, in corresponding holes 68. The upper guide rods 6969 carry a set of loosely mounted spacing plates 70 of uniform thickness and corresponding in number to the corrugation of the tube. to be compressed and are provided with corresponding holes '71-'71 (see left side of Figs. 9- and.12) which are spaced by springs 72 at a distance corresponding to the pitch of the corrugatedtube 10a. The forming plates '70 are provided with semicircular openings 79 which correspond .to the smallest diameter of the corrugated tube.

In a similar way the lower guide rods 69' -69 carry a set of spacing plates 70 (see right side of Fig. 9).

To insert a tube for its compression, the base blocks are unhooked and the upper base block 65 swung upwardly. The tube is now inserted in 11 the lower base block 65' so that its conical head 12 comes to rest in the lower half of the corresponding recess 66 with its stem 13 resting in the lower half of the hole 67. At the same time the threaded portion 39 of the tube comes to rest between and on the lower spacer plates 70' whereby the lower half of each corrugation lies between two spacing plates 70' and'rests with its portions of smallest diameter in the apertures '79 of the plates 70. The base is closed, by swinging its upper part 65 into the position shown in Fig. 11, and in so doing the upper spacing plates 70 as shown on the left side of Fig. 9 engage the upper half of the tube 10ain a similar way as previously described in connection with the lower spacing plates '70 in reference to the lower half of the tube. The base blocks are then looked together by means of the hook 81. 4

An end-block '16 provided withfour holes 77 registering with the guide rods 69 and 69 is slipped over the end of the guide rods; the compression device is then placed in a suitable press and an endwise pressure applied to the block 76. This causes the block '16 to slide on the guide rods toward the base blocks 6565' thereby compressing by means of the spacer plates 70 and 70, the corrugations of the tube so that the latter assumes the shape as shown as 10b in Figs. 4 and 10.

In case I desire to compress a tube to a very small pitch and prevent the possibility of', the threads closing up inside of the tube, I have found it advantageous to provide spacing means also for the inside of the tube. For example, I insert in the tube a resilient helix 73 attached to a plug '74 (as shown in Fig. 9). The coiis of the helix 73 normally assume a spacing which corresponds to the corrugations of the noncompressed tube 10a and permit the helix to be easfly screwed in the tube. I prefer also to insert in the tube 100: a mandrel 75 having a diameter slightly less than the smallest inside diameter of the tube, for proper location of the helix 73.

It should be well understood that in this case in compressing the tube 10a, pressure is exerted both on the end-block 76 as well as the helix plug 74, so that the two move in unison; no pressure however is exerted on the mandrel '75.

It should be also understood that the helix '73 after it has been compressed with the tube, can be easily unscrewed from the latter.

As an'example of illustration, if an aluminum tube' of about 10" length, 1%" outside diameter and -.0l5" wall thickness is corrugated by my wire threading process so as to have approximately twenty-two corrugations of a depth of 1%", the tube in this process will be reduced to a length of approximately 6 /4"; if I now subject such a corrugated tube to my compression process using .040" thick spacer plate and a helix ofabout the same thickness, I obtain as final product a corrugated tube only about 2 long with corrugations having substantially rectangular profiles.

The articles obtained by the process described in this application are claimed in my copending application Ser. No. 571,905, filed October 29, 1931, which application is a division of the present application.

While I have described my invention in connection with the manufacture of helical corrugated tubes, made of hollow aluminum cylinders and used for anodes of electrolytic condensers, it should be well understood that my invention has a wide scope of application and is not limited thereto. It can be applied to variously shaped tubes made 01 different metals and the individual steps here described can be used individually or combined, without departure from the scope of my invention. Therefore, I do not wish to be limited to the specific processes and specific constructions shown and described above, but wish the appended claims to be construed as broadly as permissible in view of the prior art.

What I now claim as new and desire to secure by Letters Patent is:

1. A device for the compression of corrugated tubes, comprising a set of spacing plates normally held apart by resilient means, a fixed member on one end of the set and a movable member on the other end of the set, whereby when a corrugated blank is placed in said device and linear pressure exerted on said movable member, the spacing plates are moved toward the fixed member and cause compression of the corrugated tube, and spacing means to be inserted within said blank to limit the clearance between the corrugations on the inside of the tube.

2. A device for the compression of corrugated tubes, comprising a set of self-alining spacing plates of uniform thickness normally held apart by resilient means, a fixed member on one end of the set and a movable member on the other end of the set, whereby when a corrugated blank is placed in said device and linear pressure exerted on said movable member, the spacing plates are moved toward the fixed member and cause compression of the corrugated tube, means to guide the spacing plates in such movement, and spacing means tcbe inserted within said blank to side edge adapted to embrace the root of the corlimit the clearance between the corrugations on the inside of the tube.

3. In a device for compressing corrugated tubes, a base longitudinally and centrally divided into two base blocks, said base being provided with a seat for one end of the corrugated tube, a compression head mounted in movable relation to the base for exerting pressure on the tube, pairs of spacing members mounted in fixed vertical relation, with the upper and lower base block respectively, said spacer members being provided with substantially semi-circular apertures on the inside edge adapted to embrace the root of the corrugated tube, said spacing members being selfalining and movable toward the base upon movement of the pressure head for compressing the tube and thereby determining the clearance between the exterior corrugations of the tube.

4. In a device for compressing corrugated tubes, a base longitudinally andcentrally divided into two base blocks, said base being provided with a seat for one end of the corrugated tube, a compression head mounted in movable relation to the base for exerting pressure on the tube, pairs of spacing members mounted in fixed vertical relation with the upper and lower base block respectively resilient means between the spacer members, said spacer members being provided with substantially semi-circular apertures on the inrugated tube, said spacing members being selfalining and movable toward the base upon movement of the pressure head for compressing the tube and thereby determining the clearance between the exterior corrugations of the tube, and means to determine the clearance between the corrugations on the inside of the tube.

5. In the manufacture of corrugated tubes from a cylindrical blank, a process which comprises progressively winding a tensioned wire about the blank to form corrugations therein.

6. In the manufacture of corrugated tubes from a cylindrical blank, a process which comprises rotating said blank on a mandrel and progressively winding a tensioned wire about the rotating blank to form corrugations therein.

7. In the manufacture of corrugated tubes from acylindrical blank, a process which comprises inserting a threaded mandrel into said blank and pressing the walls of the blank into the threads of the mandrel by progressively winding a tensioned wire about the blank.

8. In the manufacture of corrugated tubes from a cylindrical blank, a process which comprises progressively winding a tensioned wire about the blank to form corrugations therein, and gradually increasing the tension of said wire in the initial steps of the winding, and maintaining the tension uniform subsequently thereto.

9. In the manufacture of corrugated tubes from a cylindrical blank, a process which comprises tensioning a wire from a fixed point and progressively winding said tensioned wire about the blank to form corrugations therein.

10. In the manufacture of corrugated tubes 140 from a blank, a process which comprises placing said blank 'on a rotatable arbor, anchoring one end of a wire so as to rotate it with said blank and said arbor, providing tensioning means at from a cylindrical blank, a process which comform helical corrugations therein corresponding to the pitch of said screw arbor.

12. In the manufacture of corrugated tubes from a cylindrical blank, a process which comprises placing said blank on a rotating mandrel,

progressively winding a tensioned wire about said blank to form corrugations therein while rotating the mandrel, reversing rotation of the mandrel to unwind the wire and smoothing out the irregularities of the corrugations by means of a smoothing roller following the unwinding wire and moving in unison therewith.

13. In the manufacture of corrugated tubes from a cylindrical blank, a process which comprises progressively winding a tensioned Ewire about the blank to form comparatively widely spaced corrugations therein and subsequently subjecting the corrugated tube to linear compression for lessening the spacing of said corrugations.

14. In the manufacture of corrugated aluminum tubes from a blank, a process which comprises progressively winding a tensioned wire about the blank to form relatively widely spaced corrugations therein and subjecting said blank to linear compression until the corrugations are closely spaced and the internal and external clearances between the corrugations are substantially the same.

15. In the manufacture of corrugated aluminum tubes from a cylindrical blank, a process which comprises progressively winding a tensioned wire about the blank to form relatively widely spaced corrugations therein, the depth of which is approximately one-half of the radius of the tube, and subjecting said corrugated tube to linear compression to obtain closely spaced corrugations of narrow and substantially rectangular profile.

16. In the manufacture of corrugated aluminum tubes from a cylindrical blank, a process which comprises progressively winding a tensioned wire about the blank to form corrugations, the depth of which approximates one-half of the radius of the blank.

17. In the manufacture of corrugated aluminum tubes from a blank, a process which comprises progressively winding a tensioned wire about the blank to form corrugations therein, the depth of which is in excess of one-eighth of one inch.

18. In the manufacture of corrugated tubes from a cylindrical blank, a process which comprises progressively winding a tensioned wire about the blank to form corrugations therein the depth of which is in excess of one-eighth of an inch, and subsequently subjecting said corrugated blank to linear compression to obtain more than five corrugations per linear inch, the total surface area of the tube remaining unchanged during said corrugating and compressing process.

19. In the manufacture of corrugated tubes from a cylindrical blank, a process which comprises progressively winding a tensioned wire about the blank to form corrugations therein in such a manner that the material is caused to freely flow from the free end of the tube and that the corrugations are formed without changing the original area of the tube.

20. In the manufacture of corrugated aluminum tubes from a cylindrical blank, a process which comprises progressively winding a tensioned wire about the blank and subsequently MAX KNAB. 

